Shading on PV panels by mast and boom.

[TrollerJoey]

Wondering how other people have approached shading from mast and boom. I am thinking of having two charge controllers. One for port and another for starboard panels. Then paralleling the outputs. My panels are mounted on the rail by the stern and pivot up when in use. The existing system is old and not working well (I recently bought the boat) so plan to replace it.

 

[SolarRat]

If your panels are wired in series right now, try wiring them in parallel instead. If in series, neither panel will output much when one is shaded. When in parallel, only the shaded panel would be affected. Two CC's are a good option if needed, and may work better...but I think it will be about the same as having your paralleled panels to one good controller...?

 

[TrollerJoey]

Thanks SolarRat, but I plan to build a 24 volt system. 12 volt panels have too low a voltage in parallel. I would need at least 2 in series to get a high enough voltage. The 24 volt panels are too big physically for where they would be mounted.

 

[SolarRat]

Thanks SolarRat, but I plan to build a 24 volt system. 12 volt panels have too low a voltage in parallel. I would need at least 2 in series to get a high enough voltage. The 24 volt panels are too big physically for where they would be mounted.

Well, if you are going to be using 12v panels they will need to be in series. But two controllers won't help if you only have two 12v panels, one on each side. What am I missing? How many panels are you planning on using? I was assuming, by your two controller idea, that port and starboard can both provide 24v independently to each CC (or the same CC). Boost CC's can be used to bump the 12v to 24v, but that is not ideal. Need more info on your current setup and planned future setup (how many panels and what size).

 

[TrollerJoey]

Four 100 watt 12 volt panels. Two on each side of the boat. So, each controller would have 2 panels on it.

 

[SolarRat]

Four 100 watt 12 volt panels. Two on each side of the boat. So, each controller would have 2 panels on it.

That will work just fine. I think you might get the same result with just 1 CC.... With the two panels on each side wired in series (24v), then both sides connected in parallel for 24v before the CC. The two on one side being shaded shouldn't affect the two on the other side with them parallel. But nothing wrong with using two CC's, especially on a boat where redundancy is a bonus.

 

[TrollerJoey]

Aha! Didn't thought of that. Another thing is that lower amp ratings are much cheaper.

 

[Danny]

Your idea to have 2 mppt charge controllers is best practice because shading is a big issue. I would wire in parallel if you think shading will be an issue on each side. Here is a video that looks at shading parallel vs series.

 

[Dzl]

Your idea to have 2 mppt charge controllers is best practice because shading is a big issue. I would wire in parallel if you think shading will be an issue on each side. Here is a video that looks at shading parallel vs series.

@Danny I have heard this said before but I haven't heard the reasoning behind it or seen any data or comparative experiments showing what sort of gains can be achieved with multiple SCCs. Have you come across anything like that?

 

[Danny]

@Danny I have heard this said before but I haven't heard the reasoning behind it or seen any data or comparative experiments showing what sort of gains can be achieved with multiple SCCs. Have you come across anything like that?

I have a small boat with limited space for panels. The mast has lines on it. Boats park next to me etc. I have 2 mppt cc, 1 for each panel and I need it in my case because the shading kills the production of a panel.

 

[Dzl]

I have a small boat with limited space for panels. The mast has lines on it. Boats park next to me etc. I have 2 mppt cc, 1 for each panel and I need it in my case because the shading kills the production of a panel.

I hear you, I'm just curious what sort of difference might be seen between 2 panels, parallel connected, and 2 panels each with their own mppt controller. I've been asking around and haven't come across any solid data yet.

 

[Danny]

I hear you, I'm just curious what sort of difference might be seen between 2 panels, parallel connected, and 2 panels each with their own mppt controller. I've been asking around and haven't come across any solid data yet.

I think in general it depends on the amount and cell pattern of the shading you expect. This is predictable for trees or vent pipes on a house but it random on a sailboat on the sea / at anchor. I can just look at the parallel video with no shade and expect that would be my output vs the shaded parallel output if I had 2 ccs in certain cases.

 

[TrollerJoey]

Shading is a big problem. I have a 3000 watt grid tied system on my house. A palm tree grew up enough to shade a small part of the panels, I was only getting around 700 watts where normally I get max of 3100 watts. One way to avoid this is to have individual micro-inverters on each panel. I don't know if there is something similar for mppt charge controllers. I imagine that having one CC per panel would be equivalent to micro-inverters for a grid tied system. If that was done, would you need to isolate each CC? A diode between the CC and the battery?

 

[Danny]

Shading is a big problem. I have a 3000 watt grid tied system on my house. A palm tree grew up enough to shade a small part of the panels, I was only getting around 700 watts where normally I get max of 3100 watts. One way to avoid this is to have individual micro-inverters on each panel. I don't know if there is something similar for mppt charge controllers. I imagine that having one CC per panel would be equivalent to micro-inverters for a grid tied system. If that was done, would you need to isolate each CC? A diode between the CC and the battery?

The ccs are self isolating and join together in a network to share the job of charging maintaining load power. I have victron mppt for my boat . Like you say it is the same as the enphase iq7a iq7plus on my house. These are efficient, diodes have voltage drop and are not as efficient as microcontroller mppt based solutions needed for your palm tree issue but boat shading for me is 100 x more complicated. MPPTs at low watts are pretty cheap. Here is a video of my solar project and the networking of mppt.

smart battery sense networking

. Solar project w/ mppt

 

[TrollerJoey]

Awesome! Thanks. Some good ideas there. I will be going with the solid frame panels, mostly for the cost. Using 2 mppt controllers looks like the best option. It's a fair distance from my panels to where the batteries are, so will be interesting to see what the voltage drop will be. There is existing wiring, #6 I think. Crazy how a few millivolts have such a big effect. I come from the commercial fishing side of things in marine. If there was a problem you just got a bigger alternator and more batteries. Worrying about a few millivolt drop was laughable.

 

[Danny]

Awesome! Thanks. Some good ideas there. I will be going with the solid frame panels, mostly for the cost. Using 2 mppt controllers looks like the best option. It's a fair distance from my panels to where the batteries are, so will be interesting to see what the voltage drop will be. There is existing wiring, #6 I think. Crazy how a few millivolts have such a big effect. I come from the commercial fishing side of things in marine. If there was a problem you just got a bigger alternator and more batteries. Worrying about a few millivolt drop was laughable.

The 200mv issue is only a big issue in my estimation at sunset when using Lifepo4. The 200mv between 13.6 and 13.8 is quite a bit of power using lifepo4 at sun down. #6 is plenty big but the multiple mppts can cause voltage reading issues in my experience. Rigid panels are the way to go for durability if you have room. Good luck with your project. Danny

 

[TrollerJoey]

Thanks for your input Danny.

 

[Mosslandingcreatures@gmai]

That will work just fine. I think you might get the same result with just 1 CC.... With the two panels on each side wired in series (24v), then both sides connected in parallel for 24v before the CC. The two on one side being shaded shouldn't affect the two on the other side with them parallel. But nothing wrong with using two CC's, especially on a boat where redundancy is a bonus.

Look on the back of your panels they will list output voltage. Put in one side of the boat 2 of them in series. Do the same for the other side of the boat. now you decide one mppts or two. Victron’s are very smart. I decided on two of them because my wire sizes were smaller and one side of the boat is uneffected by the other side. Get yourself set up with a gyb preventer which you can draw at max to starboard or port.

 

[Mosslandingcreatures@gmai]

Gbye preventer attached to the boom to swing it out of the way so you have only the mast to contend with shading.